ES2725477T3 - Power supply system and power supply procedure - Google Patents

Abstract

A power supply system, comprising: a chain of photovoltaic panels (10), an inverter (20) and a transformer (30), in which an input end of the inverter (20) is connected to an output end of the chain of photovoltaic panels (10), an output end of the inverter (20) is connected to an input end of the transformer (30) and an output end of the transformer (30) is configured to provide a supply voltage, wherein the power supply system further comprises a voltage controller (40), wherein the voltage controller (40) comprises: a first sampling unit (404), a control unit (405) connected to the first unit sampling (404) and an inverting unit (406) connected to both the first sampling unit (404) and the control unit (405); and the voltage controller (40) further comprises: a first terminal (401), a second terminal (402) and a third terminal (403), in which one end of the first terminal (401) is connected to a first end of output of the inverter unit (406), the other end of the first terminal (401) is connected to a first output end of the inverter (20), one end of the second terminal (402) is connected to a second output end of the inverter unit (20), the other end of the second terminal (402) is connected to a second output end of the inverter (20), one end of the third terminal (403) is connected to a third output end of the inverter unit ( 406), and the other end of the third terminal (403) is connected to a third output end of the inverter (20); The inverter unit (406) comprises: an energy storage circuit (406a), a primary circuit (406b) connected to the energy storage circuit (406a) and a filter circuit (406c) connected to the primary circuit (406b); The first sampling unit (404) is configured to sample an initial voltage of a neutral point of the energy storage circuit (406a) of the inverter unit (406); The control unit (405) is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation signal, PWM, provided by the control unit (405 ), and turn on / off the switching transistors of the primary circuit (406b) of the inverter unit (406) in accordance with the PWM signal in order to control the inverter unit (406) to provide a first alternating current voltage across of the filter circuit, where the first voltage is a ground voltage of the chain of photovoltaic panels (10) connected to the input end of the inverter (20); and the inverter unit (406) is configured to provide the first alternating current voltage under the control of the control unit (405); and if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter (20), the control unit (405) controls the energy storage circuit ( 406a) for discharge, to reduce a voltage of a neutral point of an AC side of the inverter (20); or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit (405) controls the energy storage circuit (406a) for charging, to Increase the voltage of the neutral point of the AC side of the inverter (20), where the AC side of the inverter (20) is one side of the inverter (20) to provide an AC voltage.

Description

DESCRIPTION

Power supply system and power supply procedure

Technical field

The present invention relates to the photoelectric field and, in particular, to an energy supply system and an energy supply method.

Background

A photovoltaic power generation system generally includes photovoltaic panels, an inverter, a transformer and other devices. A positive electrode and a negative electrode of a photovoltaic panel are connected to two input ends of the inverter. The inverter has three output ends connected to the transformer and provides a three-phase alternating current. Generally, photovoltaic panels are classified into a P-type photovoltaic panel and an N-type photovoltaic panel. When a voltage between a negative electrode of the P-type photovoltaic panel and ground is negative, or when a voltage between a positive electrode of the panel Type N photovoltaic and ground is positive, there is a degradation of the output power of the photovoltaic panel. This is called the potential induced degradation effect (PID) of the photovoltaic panel.

To suppress the PID effect of the photovoltaic panel, a circuit shown in FIG. 1 is used in the prior art. A direct current voltage source is connected between a negative electrode of a chain of photovoltaic panels of type P and ground to increase a negative voltage between the negative electrode of the chain of photovoltaic panels of type P and earth, or a voltage source Continuous is connected between a positive electrode of a chain of photovoltaic panels of type N and ground to reduce a positive voltage between the positive electrode of the chain of photovoltaic panels of type N and earth, in order to suppress the PID effect of the chain of photovoltaic panels.

When the voltage between the positive electrode or the negative electrode of the photovoltaic panel and ground is controlled by the procedure, the positive electrode or the negative electrode of each photovoltaic panel must be connected to a continuous voltage source using a cable, which results in an increase in cable costs and a relatively complex wiring.

Document CN101931238A refers to the field of "arrangements or systems of electrical power supply or distribution circuits and electrical energy storage systems". The invention discloses a microred system coordination control method that uses a storage battery energy storage system as the main energy supply. Conventional investment products and technology hardly form a micro-network and cannot meet the requirement of stable operation of the micro-network system. The microred storage battery energy storage system is used as the main power supply when the microred operates independently, the frequency and voltage of the microred are kept constant, and a distributed power supply controls the energy together with the microred voltage and a phase angle; and a microred control system controls a bi-directional inverter for energy storage to effectively switch between a parallel control mode and an independent mode of operation according to the state of an external power network. The power supply in the micro network has the advantages of high robustness, high speed and the ability to perform a bi-directional flow of electrical energy and flexible current control and to meet the requirement of stable operation of the microred system.

In the drafting of the claims, said document does not disclose:

A first sampling unit, a control unit connected to the first sampling unit and an inverting unit connected to both the first sampling unit and the control unit.

The first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit; The control unit is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation signal, PWM, provided by the control unit, and turn on / off switching transistors of the primary circuit in the inverter unit according to the PWM signal in order to control the inverter unit to provide a first alternating current voltage through the filter circuit, where the first voltage is a ground voltage of the chain of photovoltaic panels connected to the input end of the inverter; and the inverter unit is configured to provide the first alternating current voltage under the control of the control unit; and if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the control unit controls the energy storage circuit for discharge, to reduce a voltage of a neutral point on an AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the circuit of storage of energy for its load, to increase the voltage of the neutral point of the AC side of the inverter, where the AC side of the inverter is one side of the inverter to provide an AC voltage.

That is, it does not disclose:

the mode of comparing peak amplitudes and sampling involved in the control of loading and unloading (to reduce or increase the neutral point voltage).

Document CN103701150A discloses a parallel circuit of multiple units, a power supply system and a voltage regulation procedure. The multi-unit parallel circuit comprises N photovoltaic inverters that are connected in parallel, the output ends of the N photovoltaic inverters are connected to the input ends of an isolation transformer, the input ends of each of the N inverters Photovoltaic are connected to at least one cell panel, the cell panels are used to supply input voltages to the photovoltaic inverter, the output voltages of the cell panels of each photovoltaic inverter are equal, only the cathode of the first photovoltaic inverter among the N PV inverters are grounded, where N is an integer and is greater than or equal to 2; The number of cellular panels connected to the input ends of the first photovoltaic inverter is greater than the number of cellular panels connected to the input ends of any other photovoltaic inverter among the N photovoltaic inverters. By means of the technical scheme, the cathodes of the photovoltaic inverters can generate negative voltages to ground and, therefore, the technical problem that the inverters of the network connection circuit of inverters of the prior art can cause leakage is solved from current to ground.

Document US20130088086A1 refers to a circuit arrangement for a solar power plant that includes an inverter without transformers to power electric power from at least one photovoltaic generator to an alternating energy network, a galvanic separation of all lines that carry current between the inverter and the power grid, and a DC voltage source in a compensation path between an electric line on the input side of the galvanic separation and a reference potential. The DC voltage source provides a compensation voltage. The compensation path includes a DC branch and an AC branch connected in parallel. The DC voltage source is connected in series with a current sensor in the DC branch, and at least one capacitor is arranged in the AC branch. In addition, a DC contactor activated by the current sensor is arranged in the compensation path.

Summary

The embodiments of the present invention provide a power supply system and a power supply method for reducing the costs of a cable between a positive electrode or a negative electrode of a photovoltaic panel and a direct current voltage source.

To achieve the above objective the following technical solutions are used in the embodiments of the present invention.

According to a first aspect, an embodiment of the present invention provides a power supply system, which includes: a chain of photovoltaic panels, an inverter and a transformer, where an input end of the inverter is connected to an end output of the chain of photovoltaic panels, an output end of the inverter is connected to an input end of the transformer, and an output end of the transformer is configured to provide a supply voltage, where the power supply system also includes a voltage controller where

The voltage controller includes: a first sampling unit, a control unit connected to the first sampling unit and an inverting unit connected to both the first sampling unit and the control unit; Y

The voltage controller also includes: a first terminal, a second terminal and a third terminal, where one end of the first terminal is connected to a first output end of the inverter unit, the other end of the first terminal is connected to a first end output of the inverter, one end of the second terminal is connected to a second output end of the inverter unit, the other end of the second terminal is connected to a second output end of the inverter, one end of the third terminal is connected to a third output end of the inverter unit, and the other end of the third terminal is connected to a third output end of the inverter;

The inverter unit includes: an energy storage circuit, a primary circuit connected to the energy storage circuit and a filter circuit connected to the primary circuit;

the first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit; The control unit is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation signal, PWM, provided by the control unit, and turn on / off the switching transistors of the primary circuit in the inverter unit according to the PWM signal in order to control the inverter unit to provide a first alternating current voltage through the filter circuit, where the first voltage is a ground voltage of the chain of photovoltaic panels connected to the input end of the inverter; and the inverter unit is configured to provide the first alternating current voltage under the control of the control unit; Y

if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the control unit controls the energy storage circuit for discharge, to reduce a voltage of a neutral point of an AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit for its load, to increase the neutral point voltage on the AC side of the inverter, where the AC side of the inverter is one side of the inverter to provide an AC voltage.

With reference to the first aspect, in a first possible way of implementing the first aspect,

The energy storage circuit includes at least one capacitance element, where the capacitance element is directly grounded, or grounded through an inductor, or grounded through a resistor, or grounded by medium of a diode; The primary circuit is a three-phase inverter bridge circuit and is configured to convert a first DC voltage into the first AC voltage, where the first DC voltage is a voltage from the energy storage circuit; and the filter circuit is configured to provide the first alternating current voltage.

With reference to the first possible way of implementing the first aspect, in a second possible way of implementing the first aspect,

The energy storage circuit includes two capacitance elements, where the two capacitance elements are connected in series, and a midpoint between the two capacitance elements is directly connected to ground, or connected to ground by means of an inductor, or grounded through a resistor, or grounded through a diode.

With reference to the first aspect, in a third possible way of implementing the first aspect,

The inverter includes: a second sampling unit and a first communications unit connected to the second sampling unit, and the voltage controller also includes a second communications unit, where

the second sampling unit is configured to sample the ground voltage of the chain of photovoltaic panels connected to the input end of the inverter, the first communications unit is configured to communicate with the second communications unit in the voltage controller, and the The second communications unit is configured to communicate with the first communications unit in the inverter, to obtain the ground voltage of the chain of photovoltaic panels connected to the input end of the inverter.

With reference to the first aspect, or the first possible way of implementing the first aspect, or the second possible way of implementing the first aspect, in a fourth possible way of implementing the first aspect, the inverter unit is a two-level inverter circuit, or a three-level inverter circuit, or a multi-level inverter circuit.

With reference to the first aspect, in a fifth possible implementation manner of the first aspect, the power supply system includes M inverters, M photovoltaic panel chains and a voltage controller, where the M inverters are connected in parallel, one end of Each inverter's input is connected to the output end of a chain of photovoltaic panels, one output end of each inverter is connected to the input end of the transformer, a first output end of each inverter is connected to the first terminal of the voltage controller , a second output end of each inverter is connected to the second terminal of the voltage controller and a third output end of each inverter is connected to the third terminal of the voltage controller.

According to a second aspect, an embodiment of the present invention provides an energy supply method, which includes:

obtain a first voltage and an initial voltage, where the first voltage is a ground voltage of a chain of photovoltaic panels connected to an input end of an inverter, and the initial voltage is an initial voltage of a neutral point of an inverter unit in a voltage controller;

control, in accordance with the first voltage and the initial voltage, the inverter unit to provide a first alternating current voltage; Y

if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, control the inverter unit for discharge, to reduce a neutral point voltage on one side AC power of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, control the inverter unit for its load, to increase the neutral point voltage of the inverter's alternating current side, where

The AC side of the inverter is one side of the inverter to provide an AC voltage.

With reference to the second aspect, in a first possible way of implementing the second aspect, if the photovoltaic panel chain is a P-type photovoltaic panel chain, the power supply method specifically includes:

obtain a voltage between a negative electrode of the chain of photovoltaic panels of type P and ground and the initial voltage of the neutral point of the inverter unit; Y

If the voltage between the negative electrode of the P-type photovoltaic panel chain and ground is less than zero volts, adjust the on / off of power components in the inverter unit according to the initial voltage and the voltage between the negative electrode of the chain of photovoltaic panels of type P and ground, to control the inverter unit to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second voltage of alternating current, in order to charge the inverter unit, to increase the voltage of the neutral point of the inverter's alternating current side, so that the voltage between the negative electrode of the P-type photovoltaic panel chain and ground is greater than or equal to zero volts.

With reference to the second aspect, in a second possible way of implementing the second aspect, if the photovoltaic panel chain is an N-type photovoltaic panel chain, the power supply method specifically includes:

obtain a voltage between a positive electrode of the N-type photovoltaic panel chain and ground and the initial voltage of the neutral point of the inverter unit; Y

If the voltage between the positive electrode of the N-type photovoltaic panel chain and ground is greater than zero volts, adjust the on / off of power components in the inverter unit according to the initial voltage and the voltage between the positive electrode of the chain of photovoltaic panels of type N and ground, to control the inverter unit to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is greater than the peak amplitude of the second voltage of alternating current, in order to discharge the inverter unit, to reduce the neutral point voltage of the inverter's alternating current side, so that the voltage between the positive electrode of the N-type photovoltaic panel chain and ground is less than or equal to zero volts.

With reference to the second aspect, in a third possible way of implementing the second aspect, there are M inverters and M photovoltaic panel chains, the M inverters are connected in parallel, one input end of each inverter is connected to a photovoltaic panel chain , and if the photovoltaic panel chains are P-type photovoltaic panel chains, the power supply process specifically includes:

obtain voltages between negative electrodes of all P-type photovoltaic panel chains and ground and the initial voltage of the neutral point of the inverter unit; Y

If the smallest value of the voltages between the negative electrodes of all P-type photovoltaic panel chains and ground is less than zero volts, adjust the on / off of power components in the inverter unit according to the initial voltage and the smallest value of the voltages between the negative electrodes of the P-type photovoltaic panel chains and ground, to control the inverter unit to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, so that the inverter unit is charged, to increase the voltage of the neutral point of the inverter's alternating current side, and the smallest value of the voltages between the negative electrodes of the chains of photovoltaic panels of type P and ground is greater than or equal to zero volts.

With reference to the second aspect, in a fourth way of possible implementation of the second aspect, there are M inverters and M photovoltaic panel chains, the M inverters are connected in parallel, one input end of each inverter is connected to a photovoltaic panel chain , and if the photovoltaic panel chains are N-type photovoltaic panel chains, the power supply procedure specifically includes:

obtain voltages between positive electrodes of all chains of photovoltaic panels of type N and ground and the initial voltage of the neutral point of the inverter unit; Y

If the highest value of the voltages between the positive electrodes of all the N-type photovoltaic panel chains and ground is greater than zero volts, adjust the on / off of power components in the inverter unit according to the initial voltage and the highest value of the voltages between the positive electrodes of the N-type photovoltaic panel chains and ground, to control the unit inverter to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is greater than the peak amplitude of the second alternating current voltage, in order to discharge the inverter unit, to reduce the voltage of the neutral point of the AC side of the inverter, so that the highest value of the voltages between the positive electrodes of the N-type photovoltaic panel chains and ground is less than or equal to zero volts. In accordance with the power supply system and the power supply method provided in the embodiments of the present invention, the power supply system includes: a chain of photovoltaic panels, an inverter and a transformer. An input end of the inverter is connected to an output end of the chain of photovoltaic panels, an output end of the inverter is connected to an input end of the transformer, and an output end of the transformer is configured to provide a voltage of supply. The power supply system also includes a voltage controller. The voltage controller includes: a first sampling unit, a control unit connected to the first sampling unit and an inverting unit connected to both the first sampling unit and the control unit. The voltage controller also includes: a first terminal, a second terminal and a third terminal. One end of the first terminal is connected to a first output end of the inverter unit, and the other end of the first terminal is connected to a first output end of the inverter. One end of the second terminal is connected to a second output end of the inverter unit, and the other end of the second terminal is connected to a second output end of the inverter. One end of the third terminal is connected to a third output end of the inverter unit, and the other end of the third terminal is connected to a third output end of the inverter. The inverter unit includes: an energy storage circuit, a primary circuit connected to the energy storage circuit and a filter circuit connected to the primary circuit. The first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit. The control unit is configured to control, according to a difference between the initial voltage and the first voltage, the switching on / off of switching transistors of the primary circuit in the inverter unit, so that the filter circuit of the inverter unit it provides a first alternating current voltage, where the first voltage is a ground voltage of the chain of photovoltaic panels connected to the input end of the inverter. The inverter unit is configured to provide the first alternating current voltage under the control of the control unit. If a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the control unit controls the energy storage circuit for discharge, to reduce a voltage of a neutral point of an AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit for its load, to increase the neutral point voltage on the AC side of the inverter. The AC side of the inverter is one side of the inverter to provide an AC voltage. In the prior art, a positive electrode or a negative electrode of each photovoltaic panel must be connected to a direct current voltage source using a cable, which makes it relatively difficult to handle. Thanks to the solution provided by the present invention, it is not necessary to add any cables to the positive electrode or the negative electrode of the photovoltaic panel, so that the cost of the cables between devices can be reduced.

Brief description of the drawings

To more clearly describe the technical solutions of the embodiments of the present invention or of the prior art, the accompanying drawings required to describe the embodiments or prior art are briefly presented below. Obviously, the accompanying drawings of the following description simply show some embodiments of the present invention.

FIG. 1 is a schematic structural diagram of a circuit for suppressing a PID effect of a photovoltaic panel in the prior art.

FIG. 2 is a schematic diagram 1 of a power supply system according to an embodiment of the present invention.

FIG. 3 is a circuit diagram 1 of an inverter unit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram 2 of a power supply system according to an embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram of a power supply system in accordance with an embodiment of the present invention.

FIG. 6 is a circuit diagram 2 of an inverter unit according to an embodiment of the present invention.

FIG. 7 is a circuit diagram 3 of an inverter unit according to an embodiment of the present invention.

FIG. 8 is a circuit diagram 4 of an inverter unit according to an embodiment of the present invention.

FIG. 9 is a schematic diagram 3 of a power supply system according to an embodiment of the present invention.

FIG. 10 is a schematic flow chart 1 of a power supply method according to an embodiment of the present invention.

FIG. 11 is a schematic flow diagram 2 of a power supply method according to an embodiment of the present invention.

FIG. 12 is a schematic flow chart 3 of a power supply method according to an embodiment of the present invention.

FIG. 13 is a schematic flow chart 4 of a power supply method according to an embodiment of the present invention.

Description of embodiments

The technical solutions of the embodiments of the present invention are clearly described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are simply a part of, and not all, the embodiments of the present invention.

An embodiment of the present invention provides a power supply system. As shown in FIG. 2, the power supply system includes: a chain of photovoltaic panels 10, an inverter 20 connected to the chain of photovoltaic panels 10 and a transformer 30 connected to the inverter 20. The chain of photovoltaic panels 10 provides a direct current voltage to the inverter 20 through a positive electrode a and a negative electrode b of the chain of photovoltaic panels 10, and the inverter 20 converts the direct current voltage into an alternating current voltage, and provides the alternating current voltage to the transformer 30 through of an output end of alternating current voltage of the inverter 20.

The power supply system further includes a voltage controller 40. The voltage controller 40 includes: a first terminal 401, a second terminal 402, a third terminal 403, a first sampling unit 404, a control unit 405 connected to the first sampling unit 404 and an inverter unit 406 connected to both the first sampling unit 404 and the control unit 405.

One end of the first terminal 401 is connected to a first output end of the inverter unit, and the other end of the first terminal 401 is connected to a first output end 201 of the inverter. One end of the second terminal 402 is connected to a second output end of the inverter unit, and the other end of the second terminal 402 is connected to a second output end 202 of the inverter. One end of the third terminal 403 is connected to a third output end of the inverter unit, and the other end of the third terminal 403 is connected to a third output end 203 of the inverter. When the voltage controller 40 is discharged through an energy storage circuit in the inverter unit, the voltage controller 40 provides electrical power to one side of the inverter's alternating current (i.e., one side of the inverter to provide the voltage alternating current) through the first terminal 401, the second terminal 402 and the third terminal 403. When the voltage controller 40 loads the energy storage circuit in the inverter unit from the AC side of the inverter, the power controller voltage 40 receives electrical energy introduced from the AC side of the inverter, through the first terminal 401, the second terminal 402 and the third terminal 403.

The inverter unit 406 can be a two-level inverter circuit, a three-level inverter circuit or a multi-level inverter circuit. A description is provided using an example in which the inverter unit 406 is a two-level inverter circuit. As shown in FIG. 3, the inverter unit 406 includes: an energy storage circuit 406a, a primary circuit 406b and a filter circuit 406c. An input end of the primary circuit is connected to an output end of the energy storage circuit, an output end of the primary circuit is connected to an input end of a filter circuit.

The voltage controller 40 further includes: the first sampling unit 404, configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit; the control unit 405, connected to the first sampling unit 404 and configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a PWM signal (pulse width modulation), provided by the control unit, and switching on / off switching transistors of the primary circuit in the inverter unit according to the PWM signal in order to control the inverter unit to provide a first alternating current voltage through the filter circuit, where the first voltage is a ground voltage of the photovoltaic panel chain 10 connected to an input end of the inverter twenty; and the inverter unit 406, connected to both the control unit 405 and the first sampling unit 404 and configured to provide the first alternating current voltage under the control of the control unit 405; where if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the energy storage circuit is discharged, to reduce a voltage of a neutral point of the AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the energy storage circuit is charged, to increase the neutral point voltage of the alternating current side of the inverter, where the AC side of the inverter is the side of the inverter to provide the AC voltage.

The input end of the primary circuit is connected to the output end of the energy storage circuit, and the output end of the primary circuit is connected to the input end of the filter circuit. The energy storage circuit 406a includes at least one capacitance element, configured to exchange energy with the AC side of the inverter (i.e., the output end of the AC voltage of the inverter 20) by loading and unloading processes. . The at least one capacitance element can be connected directly to ground, or connected to ground by means of an inductor, or connected to ground by means of a resistor, or connected to ground by means of a diode. This is not limited in the present invention. The primary circuit 406b is a three-phase inverter bridge circuit, includes multiple power tubes and is configured to turn on / off as indicated by the PWM signal (pulse width modulation) generated by the control unit 405, and to convert a voltage from the capacitance element in an alternating current voltage in the discharge process of the capacitance element. The filter circuit 406c is configured to rectify and filter the alternating current voltage generated by the primary circuit 406b and provide the first alternating current voltage.

In addition, as shown in FIG. 4, in the power supply system provided in this embodiment of the present invention, the inverter 20 includes a second sampling unit 204, configured to sample the ground voltage of the chain of photovoltaic panels 10 connected to the input end of the inverter 20, and the inverter 20 further includes: a first communication unit 205, connected to the second sampling unit 204, and configured to communicate with the voltage controller 40. Specifically, the first communication unit 205 is configured to communicate with a second communications unit 407 in the voltage controller 40 and transmitting the ground voltage of the chain of photovoltaic panels 10 obtained by sampling by the second sampling unit 204 to the second communications unit 407 in the voltage controller 40.

The voltage controller 40 further includes a second communications unit 407, configured to communicate with the first communications unit 205 in the inverter 20, to obtain the ground voltage of the chain of photovoltaic panels 10 connected to the input end of the inverter 20 .

The first communications unit 205 and the second communications unit 407 can communicate via PLC (communication via power line, communication via power line carrier), wireless communication or RS485 communication. This is not limited in the present invention.

For example, when the inverter unit 406 is a two-level inverter circuit, the circuit diagram of the power supply system is shown in FIG. 4. Specifically, a process in which the inverter unit 406 adjusts the neutral point voltage of the inverter's alternating current side by providing the first alternating current voltage is as follows:

The primary circuit 406b includes six power tubes, and the six power tubes form a three-phase inverter bridge circuit. S1 and S2 are switched on complementary to each other to provide an alternating current voltage Uao. S3 and S4 are complementary to each other to provide an alternating current voltage Ubo. S5 and S6 turn on in a complementary manner to each other to provide an alternating current voltage Uco. Specifically, Uao, Ubo and Uco are alternating current voltages in the form of a sine wave. When the alternating current voltage Uao provided by the inverter unit 406 and an alternating current voltage Ua provided by the inverter 20 have the same amplitudes, frequencies and phases, the alternating current voltage Ubo provided by the inverter unit 406 and a voltage of alternating current Ub provided by the inverter 20 have the same amplitudes, frequencies and phases, and the alternating current voltage Uco provided by the inverter unit 406 and an alternating current voltage Uc provided by the inverter 20 have the same amplitudes, frequencies and phases , the power supply system is in a stable state. An equivalent circuit of the power supply system is shown in FIG. 5. The exchange between the energy of the energy storage circuit 406a and the energy of the AC side of the inverter can occur when changing the amplitudes of Uao, Ubo and Uco, and because a negative electrode of a capacitor of the circuit of 406a energy storage is grounded, the neutral point voltage on the side of The inverter's alternating current can be modified by changing the capacitor voltage of the energy storage circuit.

It should be noted that a PLC communication device can be integrated in the second communication unit 407. The PLC communication device is connected to the inverter 20 in the power supply system. The second communications unit 407 communicates with a PLC communications apparatus of the first communications unit 205 in the inverter 20 using a carrier modulation circuit, to read the ground voltage of the chain of photovoltaic panels 10 connected to two ends input of the inverter 20. In an example in which the chain of photovoltaic panels 10 is a photovoltaic panel of type P, a voltage between a negative electrode of the chain of photovoltaic panels 10 and ground (i.e., a voltage between an electrode negative of the P-type photovoltaic panel and ground) that is read by the second communications unit 407 through the first communications unit 205 is -400 volts, a sampling result of sampling the initial voltage (half of a voltage in two ends of a capacitor C1 in the energy storage circuit 406a) of the neutral point of the inverter unit 406 by the first sampling unit 404 is -300 vol uncles, and the control unit 405 controls the PWM signal according to the difference (the difference here is 100 volts, ie -300 minus -400 = 100 volts) between the initial voltage and the ground voltage of the chain photovoltaic panels 10 read by the second communications unit 407, in order to reduce the amplitudes of the output voltages (i.e. the first alternating current voltages) Uao, Ubo and Uco of the inverter unit 406, so that the Power from the AC side of the inverter flows to the voltage controller 40 to charge the energy storage circuit 406a, and the voltage at both ends of the capacitor C1 increases. When a voltage charged from the two ends of the capacitor C1 to the neutral point reaches -400 volts, the control unit 405 controls the PWM signal, so that an energy balance is reached between the voltage controller 40 and the current side alternating of the inverter, thus maintaining a stable state. It should be noted that when the power supply system is in the stable state, the neutral point voltage of the inverter's alternating current side is the same as a voltage at a midpoint of the capacitor in the energy storage circuit 406, and A voltage at a midpoint of the chain of photovoltaic panels is also the same as the voltage of the neutral point of the AC side of the inverter. Therefore, the neutral point voltage of the AC side of the inverter is finally reduced from -300 volts to -400 volts by the process, so that the voltage between the negative electrode of the P-type photovoltaic panel and ground increases from -400 volts to 0 volts, thus suppressing a PID effect of the type P photovoltaic panel.

It should be noted that, in a general power supply system, a voltage of a neutral point of a power grid, a voltage of a neutral point of an AC side of an inverter and a voltage of a neutral point of a chain of photovoltaic panels are identical. The neutral point refers to a reference point of all voltage values in the power supply system. For example, when a mains supply voltage is an alternating current voltage of 220 volts, a reference point for the alternating current voltage of 220 volts is ground. That is, generally, a neutral point of the power supply system is ground, and a neutral point voltage is 0 volts.

In addition, in the general power supply system, assuming that a direct current voltage between the positive electrode and the negative electrode of the P-type photovoltaic panel chain is 800 volts, because the neutral point voltage in the Power supply system is 0 volts, a positive electrode voltage of the P-type photovoltaic panel chain is 400 volts and a negative electrode voltage is -400 volts. Consequently, there is a negative voltage of -400 volts between the negative electrode of the chain of photovoltaic panels and ground, which causes degradation of the power of the chain of photovoltaic panels.

In addition, in the power supply system provided in this embodiment of the present invention, the voltage controller is added. After the power supply system provided in this embodiment of the present invention begins operating, first, the power storage circuit of the voltage controller is charged, so that the first alternating current voltage provided by the inverter unit is the same as the second alternating current voltage provided by the inverter (where the amplitudes, phases and frequencies of the voltages are all the same). Generally, a voltage value of the energy storage circuit is approximately twice a peak amplitude of the supply voltage of the mains. It is assumed that when the voltage at the two ends of the capacitor in the power storage circuit is -500 volts, the power supply system reaches the stable state. Because the neutral point voltage of the energy storage circuit is half of the total capacitor voltage of the energy storage circuit, the neutral point voltage of the energy storage circuit is -250 volts.

In this case, the ground voltage of the P-type photovoltaic panel chain is compensated. For example, the control unit determines, according to a difference of 150 volts between the initial voltage of -250 volts and the first voltage of -400 volts, the duty cycle of the PWM signal provided by the control unit, and turns on / off, using the PWM signal, the switching transistors of the primary circuit of the inverter unit to reduce the amplitude of the first current voltage alternate provided by the inverter unit through the filter circuit, so that the energy from the AC side of the inverter flows to the voltage controller to charge the energy storage circuit of the inverter unit. When the neutral point voltage of the Power storage circuit increases from -250 volts to -400 volts (that is, the voltage at the two ends of the capacitor in the power storage circuit is -800 volts), the control unit adjusts the duty cycle of the PWM signal, so that an amplitude value of the first alternating current voltage is the same as an amplitude value of the energy storage circuit voltage. In this case, the neutral point voltage of the inverter's alternating current side is -400 volts, and a balance is reached between the voltage of the inverter's alternating current side and the voltage provided by the voltage controller.

It should be added that increasing the voltage of the neutral point of the energy storage circuit in the voltage controller to -400 volts is equivalent to synchronously increasing the voltage of the neutral point of the power supply system, the voltage of the neutral point of the side of alternating current of the inverter and the neutral point voltage of the chain of photovoltaic panels of type P at -400 volts, so that the voltage between the negative electrode of the chain of photovoltaic panels of type P and earth increases to zero, thus reducing The power consumption of the P-type photovoltaic panel. It should be noted that, if the photovoltaic panel is a P-type photovoltaic panel, the first alternating current voltage provided by the voltage controller adjusts the neutral point voltage of the alternating current side. of the inverter, so that a voltage between a negative electrode of the P-type photovoltaic panel and ground is greater than or equal to zero volts; or if the photovoltaic panel is an N-type photovoltaic panel, the first alternating current voltage provided by the voltage controller adjusts the neutral point voltage of the inverter's alternating current side, so that a voltage between a positive electrode of the panel Type N photovoltaic and ground is less than or equal to zero volts.

In another example, the energy storage circuit 406a of the inverter unit 406 may also be a circuit shown in FIG. 6, which includes two capacitance elements C1 and C2. C1 and C2 are connected in series, and C2 is connected to ground by means of a resistor R or connected to ground by means of a diode.

The principle of reducing a positive voltage between the positive electrode of the N-type photovoltaic panel and ground is the same as that of increasing the negative voltage between the negative voltage of the P-type photovoltaic panel and ground, and the details are not described again. in the present document. For example, when the chain of photovoltaic panels of the power supply system in this embodiment of the present invention is a chain of photovoltaic panels of type N, the inverter unit 406 may have the structure shown in FIG. 7. A positive electrode of the capacitance element of the energy storage circuit 406a is grounded. Specifically, the positive electrode of the capacitance element is connected directly to ground, or connected to ground by means of a resistor, or connected to ground by means of an inductor, or connected to ground by means of a diode. This is not limited in the present invention.

As shown in FIG. 8, in the power supply system provided in this embodiment of the present invention, the inverter unit 406 may alternatively be a three-level inverter circuit. A midpoint between C1 and C2 is connected to ground by means of a resistor R. After the neutral points of C1 and C2 are connected to ground by means of a resistor R, if the photovoltaic panel is a photovoltaic panel of type P , and a tension at two ends of C1 is less than a tension at two ends of C2 under the control of the control unit, a difference between the tension at the two ends of C1 and the tension at the two ends of C2 is the voltage between the negative electrode of the P-type photovoltaic panel and ground; or if the photovoltaic panel is an N-type photovoltaic panel, and a voltage at two ends of C1 is greater than a voltage at two ends of C2 under the control of the control unit, a difference between the voltage at the two ends of C1 and the voltage at the two ends of C2 is the voltage between the positive electrode of the N-type photovoltaic panel and ground. That is, the circuit can not only suppress the PID effect of the P-type photovoltaic panel, but it can also suppress the PID effect of the N-type photovoltaic panel, and the circuit only needs to be controlled to operate in two different modes.

In another example, the energy storage circuit 406a of the inverter unit 406 may alternatively include multiple capacitance elements. The multiple capacitance elements have the same function as that of one or two capacitance elements in this embodiment of the present invention. This is not limited in the present invention.

An embodiment of the present invention further provides another power supply system. As shown in FIG. 9, the system includes M inverters 20, M chains of photovoltaic panels 10 and a voltage controller 40. The M inverters are connected in parallel, one input end of each inverter is connected to a chain of photovoltaic panels, and one end of AC voltage output of each inverter is connected to an AC voltage output end of the voltage controller.

In such a scenario in which there are multiple photovoltaic panels and multiple inverters, the second communication unit 407 of the voltage controller communicates with the first communication units 205 in the multiple inverters 20 to read a ground voltage that is of the chain of photovoltaic panels 10 connected to the input end of each inverter 20 and which is obtained by sampling by the second sampling unit 204. The control unit 405 controls, in accordance with the ground voltages of the multiple chains of photovoltaic panels 10 and an initial voltage (that is, the initial voltage of the neutral point of the inverter unit that is obtained through sampling by the first sampling unit), the inverter unit 406 to provide a First AC voltage. The first alternating current voltage is used to control the neutral point voltage of the inverter's alternating current side, so that a voltage between a negative electrode of each P-type photovoltaic panel and ground is greater than or equal to zero volts, or a voltage between a positive electrode of each type N photovoltaic panel and ground is less than or equal to zero volts.

An embodiment of the present invention further provides a power supply method, applied to the previous power supply system, which includes: If a chain of photovoltaic panels is a chain of photovoltaic panels of type P, a first current voltage AC provided by a voltage controller adjusts a voltage of a neutral point of an output end of AC voltage of an inverter, so that a voltage between a negative electrode of the P-type photovoltaic panel chain and ground is greater that or equal to zero volts; or if the chain of photovoltaic panels is a chain of photovoltaic panels of type N, the first alternating current voltage provided by the voltage controller adjusts the neutral point voltage of the inverter's alternating current voltage output end, so that The voltage between the positive electrode of the N-type photovoltaic panel chain and ground is less than or equal to zero volts.

Specifically, as shown in FIG. 10, if the photovoltaic panel chain is a P-type photovoltaic panel chain, the power supply procedure includes the following steps:

S101: Obtain a voltage between a negative electrode of the P-type photovoltaic panel chain and ground and an initial voltage of a neutral point of an inverter unit.

The voltage between the negative electrode of the chain of photovoltaic panels of type P and ground is obtained by sampling by a sampling unit of the inverter, and the initial voltage of the inverting unit is obtained by sampling by a sampling unit of the voltage controller .

S102: If the voltage between the negative electrode of the P-type photovoltaic panel chain and ground is less than zero volts, adjust the on / off of the power components of the inverter unit according to the initial voltage and the voltage between the negative electrode of the chain of photovoltaic panels of type P and ground, to control the inverter unit to provide the first alternating current voltage. If a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the control unit controls the energy storage circuit for discharge, to reduce the voltage from the neutral point of the AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit for its load, to increase the neutral point voltage on the AC side of the inverter. The AC side of the inverter is one side of the inverter to provide an AC voltage.

In addition, specifically, as shown in FIG. 11, if the photovoltaic panel chain is an N-type photovoltaic panel chain, the power supply procedure includes the following steps:

S201: Obtain a voltage between a positive electrode of the N-type photovoltaic panel chain and ground and an initial voltage of a neutral point of an inverter unit.

The voltage between the positive electrode of the N-type photovoltaic panel chain and ground is obtained by sampling by a sampling unit of the inverter, and the initial voltage is obtained by sampling by a sampling unit of the voltage controller.

S202: If the voltage between the positive electrode of the N-type photovoltaic panel chain and ground is greater than zero volts, adjust the on / off power components of the inverter unit according to the initial voltage and the voltage between the positive electrode of the chain of photovoltaic panels of type N and ground, to control the inverter unit to provide a first alternating current voltage. A peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage, to cause the inverter unit to discharge, to reduce the voltage of a neutral point of the inverter's alternating current side , so that the voltage between the positive electrode of the N-type photovoltaic panel chain and ground is less than or equal to zero volts. When the power supply system includes multiple inverters connected in parallel, an input end of each inverter is connected to a chain of photovoltaic panels, and an AC output voltage end of the voltage controller is correspondingly connected respectively. to one output end of alternating current voltage of each inverter, and the power supply procedure of the power supply system is as follows.

If the photovoltaic panel chains are P-type photovoltaic panel chains, the first alternating current voltage provided by the inverter unit adjusts the neutral point voltage of the inverter's alternating current voltage output end. As shown in FIG. 12, the power supply procedure specifically includes:

S301: Obtain voltages between negative electrodes of all P-type photovoltaic panel chains and ground and an initial voltage of a neutral point of an inverter unit.

The voltages between the negative electrodes of all P-type photovoltaic panel chains and ground are obtained by sampling by an inverter sampling unit, and the initial voltage is obtained by sampling by a sampling unit of the voltage controller.

S302: If the smallest value of the voltages between the negative electrodes of all P-type photovoltaic panel chains and ground is less than zero volts, adjust the power component on / off of the inverter unit according to the voltage initial and the smallest value of the voltages between the negative electrodes of the P-type photovoltaic panel chains and ground, to control the inverter unit to provide the first alternating current voltage.

A peak amplitude of the first alternating current voltage is less than a peak amplitude of a second alternating current voltage, in order to load the inverter unit, to reduce the neutral point voltage of the inverter's alternating current side, so that the smallest value of the voltages between the negative electrodes of the P-type photovoltaic panel chains and ground is greater than or equal to zero volts.

If the photovoltaic panel chains are N-type photovoltaic panel chains, the first alternating current voltage provided by the inverter unit adjusts the neutral point voltage of the inverter's alternating current voltage output end. As shown in FIG. 13, the power supply procedure specifically includes:

S401: Obtain voltages between positive electrodes of all N-type photovoltaic panel chains and ground and an initial voltage of a neutral point of an inverter unit.

The voltages between the positive electrodes of all the N-type photovoltaic panel chains and ground are obtained by sampling by a sampling unit of the inverter, and the initial voltage is obtained by sampling by a sampling unit of the voltage controller.

S402: If the highest value of the voltages between the positive electrodes of all N-type photovoltaic panel chains and ground is greater than zero volts, adjust the on / off of power components of the inverter unit according to the voltage initial and the highest value of the voltages between the positive electrodes of the N-type photovoltaic panel chains and ground, to control the inverter unit to provide the first alternating current voltage.

A peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage, to cause the inverter unit to discharge, to reduce the neutral point voltage of the inverter's alternating current side, so that the highest value of the voltages between the positive electrodes of the N-type photovoltaic panel chains and ground is less than or equal to zero volts. For example, assuming that there are three chains of photovoltaic panels, namely a chain of photovoltaic panels 1, a chain of photovoltaic panels 2 and a chain of photovoltaic panels 3, the three chains of photovoltaic panels are all P-type photovoltaic panels, a voltage between a negative electrode of the chain of photovoltaic panels1 and ground is -500 volts, a voltage between a negative electrode of the chain of photovoltaic panels 2 and ground is -400 volts, and a voltage between a negative electrode of the chain of 3 photovoltaic panels and ground is -300 volts. The second sampling unit 204 of the inverter 20 shows the voltage between the negative electrode of the chain of photovoltaic panels connected to the second sampling unit 204 and ground. The voltage controller 40 communicates with the first communications unit 205 in the inverter 20 using the second communications unit 407 to obtain the voltages between the negative electrodes of the three chains of photovoltaic panels and the earth. The control unit 405 controls, according to the smallest voltage value of -500 volts of the voltages between the negative electrodes of the three photovoltaic panels of type P and ground and a sampled value of the initial voltage by the first unit of Sampling 404, the inverter unit 406 to provide the first alternating current voltage, to increase the neutral point voltage of the inverter's alternating current side to -500 volts and optimally compensate the voltages between the negative electrodes of the three photovoltaic panels of type P and ground, so that the voltages between the negative electrodes of the three photovoltaic panels of type P and ground are all at least equal to zero volts.

In accordance with the power supply system and the power supply method provided in the embodiments of the present invention, the power supply system includes: a chain of photovoltaic panels, an inverter and a transformer. An input end of the inverter is connected At an output end of the chain of photovoltaic panels, an output end of the inverter is connected to an input end of the transformer and an output end of the transformer is configured to provide a supply voltage. The power supply system also includes a voltage controller. The voltage controller includes: a first sampling unit, a control unit connected to the first sampling unit and an inverting unit connected to both the first sampling unit and the control unit. The voltage controller also includes: a first terminal, a second terminal and a third terminal. One end of the first terminal is connected to a first output end of the inverter unit, and the other end of the first terminal is connected to a first output end of the inverter. One end of the second terminal is connected to a second output end of the inverter unit, and the other end of the second terminal is connected to a second output end of the inverter. One end of the third terminal is connected to a third output end of the inverter unit, and the other end of the third terminal is connected to a third output end of the inverter. The inverter unit includes: an energy storage circuit, a primary circuit connected to the energy storage circuit and a filter circuit connected to the primary circuit. The first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit. The control unit is configured to control, according to a difference between the initial voltage and the first voltage, the switching on / off of switching transistors of the primary circuit in the inverter unit, so that the filter circuit of the inverter unit it provides a first alternating current voltage, where the first voltage is a ground voltage of the chain of photovoltaic panels connected to the input end of the inverter. The inverter unit is configured to provide the first alternating current voltage under the control of the control unit. If a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter, the control unit controls the energy storage circuit for discharge, to reduce a voltage of a neutral point of an AC side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit for its load, to increase the neutral point voltage on the AC side of the inverter. The AC side of the inverter is one side of the inverter to provide an AC voltage. In the prior art, a positive electrode or a negative electrode of each photovoltaic panel must be connected to a direct current voltage source using a cable, which makes it relatively difficult to handle. By means of the solution provided in the present invention, it is not necessary to add any cables to the positive electrode or the negative electrode of the photovoltaic panel, so that the cost of the cables between devices can be reduced.

Those skilled in the art may understand that all or some of the steps of the procedural embodiments may be implemented by a program that commands related hardware. The program may be stored in a computer readable storage medium. When the program is executed, the steps of the procedural embodiments are carried out. The above storage medium includes any media that can store program code, such as a ROM, a RAM, a magnetic disk or an optical disk.

The above descriptions are simply specific ways of implementation of the present invention, but are not intended to limit the scope of protection of the present invention. Any variation or replacement conceived easily by those skilled in the art within the technical scope disclosed in the present invention will be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention will be subject to the scope of protection of the claims.

Claims (11)

1. A power supply system, comprising: a chain of photovoltaic panels (10), an inverter (20) and a transformer (30), in which an input end of the inverter (20) is connected to one end of output from the chain of photovoltaic panels (10), an output end of the inverter (20) is connected to an input end of the transformer (30) and an output end of the transformer (30) is configured to provide a voltage of supply, where the power supply system further comprises a voltage controller (40), in which The voltage controller (40) comprises: a first sampling unit (404), a control unit (405) connected to the first sampling unit (404) and an inverter unit (406) connected to both the first sampling unit (404) as to the control unit (405); Y The voltage controller (40) further comprises: a first terminal (401), a second terminal (402) and a third terminal (403), in which one end of the first terminal (401) is connected to a first output end of the inverter unit (406), the other end of the first terminal (401) is connected to a first output end of the inverter (20), one end of the Second terminal (402) is connected to a second output end of the inverter unit (20), the other end of the second terminal (402) is connected to a second output end of the inverter (20), one end of the third terminal ( 403) is connected to a third output end of the inverter unit (406), and the other end of the third terminal (403) is connected to a third output end of the inverter (20); The inverter unit (406) comprises: an energy storage circuit (406a), a primary circuit (406b) connected to the energy storage circuit (406a) and a filter circuit (406c) connected to the primary circuit (406b); The first sampling unit (404) is configured to sample an initial voltage of a neutral point of the energy storage circuit (406a) of the inverter unit (406); The control unit (405) is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation signal, PWM, provided by the control unit (405 ), and turn on / off the switching transistors of the primary circuit (406b) of the inverter unit (406) in accordance with the PWM signal in order to control the inverter unit (406) to provide a first alternating current voltage across of the filter circuit, where the first voltage is a ground voltage of the chain of photovoltaic panels (10) connected to the input end of the inverter (20); and the inverter unit (406) is configured to provide the first alternating current voltage under the control of the control unit (405); Y if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter (20), the control unit (405) controls the energy storage circuit (406a ) for discharge, to reduce a voltage of a neutral point on an AC side of the inverter (20); or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit (405) controls the energy storage circuit (406a) for charging, to Increase the neutral point voltage of the AC side of the inverter (20), where the AC side of the inverter (20) is one side of the inverter (20) to provide an AC voltage. 2. The power supply system according to claim 1, wherein The energy storage circuit (406a) comprises at least one capacitance element, in which the capacitance element is directly connected to ground, or connected to ground by means of an inductor, or connected to ground by means of a resistor, or grounded through a diode; The primary circuit (406b) is a three-phase bridge circuit and is configured to convert a first DC voltage into the first AC voltage, where the first DC voltage is a voltage from the energy storage circuit (406A) ; and the filter circuit (406c) is configured to provide the first alternating current voltage. 3. The power supply system according to claim 2, wherein the energy storage circuit (406a) comprises two capacitance elements, wherein the two capacitance elements are connected in series, and a midpoint between the Two capacitance elements are connected directly to ground, or connected to ground by means of an inductor, or connected to ground by means of a resistor, or connected to ground by means of a diode. 4. The power supply system according to claim 1, wherein The inverter (20) comprises: a second sampling unit and a first communications unit connected to the second sampling unit, and the voltage controller further comprises a second communications unit, in which the second sampling unit is configured to sample the ground voltage of the photovoltaic panel chain connected to the input end of the inverter (20), the first communications unit is configured to communicate with the second communications unit in the voltage controller , and the The second communications unit is configured to communicate with the first communications unit in the inverter (20), to obtain the ground voltage of the chain of photovoltaic panels connected to the input end of the inverter (20). 5. The power supply system according to any one of claims 1 to 3, wherein The inverter unit (406) is a two-level inverter circuit, or a three-level inverter circuit or a multi-level inverter circuit. 6. The power supply system according to claim 1, wherein the power supply system comprises M inverters, M photovoltaic panel chains and a voltage controller, wherein the M inverters are connected in parallel, an input end of each inverter (20) is connected to an output end of a chain of photovoltaic panels, an output end of each inverter (20) is connected to the input end of the transformer, a first output end of each inverter (20) is connected to the first terminal of the voltage controller, a second output end of each inverter (20) is connected to the second terminal of the voltage controller and a third output end of each inverter (20) is connected to the third terminal of the voltage controller tension. 7. An energy supply procedure, comprising: obtaining a first voltage and an initial voltage, in which the first voltage is a ground voltage of a chain of photovoltaic panels connected to an input end of an inverter (20), and the initial voltage is an initial voltage of a point neutral of an inverter unit (406) in a voltage controller; controlling, in accordance with the first voltage and the initial voltage, the inverter unit (406) to provide a first alternating current voltage; Y if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage provided by the inverter (20), control the inverter unit (406) for discharge, to reduce a voltage of a neutral point of an AC side of the inverter (20); or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, check the inverter unit (406) for its load, to increase the neutral point voltage of the current side inverter alternate (20), where The AC side of the inverter (20) is one side of the inverter (20) to provide an AC voltage. 8. The power supply method according to claim 7, wherein if the photovoltaic panel chain is a P-type photovoltaic panel chain, the power supply method specifically comprises: obtaining a voltage between a negative electrode of the chain of photovoltaic panels of type P and ground and the initial voltage of the neutral point of the inverter unit (406); Y If the voltage between the negative electrode of the P-type photovoltaic panel chain and ground is less than zero volts, adjust the on / off of power components in the inverter unit (406) according to the initial voltage and the voltage between the negative electrode of the chain of photovoltaic panels of type P and ground, to control the inverter unit (406) to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is less than the amplitude of peak of the second alternating current voltage, in order to charge the inverter unit (406), to increase the voltage of the neutral point of the inverter's alternating current side (20), so that the voltage between the negative electrode of the chain of photovoltaic panels of type P and ground is greater than or equal to zero volts. 9. The power supply method according to claim 7, wherein if the photovoltaic panel chain is an N-type photovoltaic panel chain, the power supply method specifically comprises: obtaining a voltage between a positive electrode of the N-type photovoltaic panel chain and ground and the initial voltage of the neutral point of the inverter unit (406); Y If the voltage between the positive electrode of the N-type photovoltaic panel chain and ground is greater than zero volts, adjust the on / off of power components in the inverter unit (406) according to the initial voltage and the voltage between the positive electrode of the chain of photovoltaic panels of type N and ground, to control the inverter unit (406) to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is greater than the amplitude of peak of the second alternating current voltage, in order to discharge the inverter unit (406), to reduce the neutral point voltage of the inverter's alternating current side (20), so that the voltage between the positive electrode of the chain of photovoltaic panels of type N and earth is less than or equal to zero volts. 10. The power supply method according to claim 7, wherein there are M inverters and M photovoltaic panel chains, the M inverters are connected in parallel, an input end of each inverter (20) is connected to a chain of photovoltaic panels (10), and if the photovoltaic panel chains are P-type photovoltaic panel chains, the power supply method specifically comprises: obtain voltages between negative electrodes of all P-type photovoltaic panel chains and ground and the initial voltage of the neutral point of the inverter unit (406); Y If the smallest value of the voltages between the negative electrodes of all P-type photovoltaic panel chains and ground is less than zero volts, adjust the on / off of power components in the inverter unit (406) according to the initial voltage and the smallest value of the voltages between the negative electrodes of all P-type photovoltaic panel chains and ground, to control the inverter unit (406) to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, in order to load the inverter unit (406), to increase the neutral point voltage of the inverter's alternating current side (20) , so that the smallest value of the voltages between the negative electrodes of the P-type photovoltaic panel chains and ground is greater than or equal to zero volts. 11. The power supply method according to claim 7, wherein there are M inverters and M photovoltaic panel chains, the M inverters are connected in parallel, one input end of each inverter (20) is connected to a supply chain. photovoltaic panels, and if the photovoltaic panel chains are N-type photovoltaic panel chains, the power supply method specifically comprises: obtain voltages between positive electrodes of all the chains of photovoltaic panels of type N and ground and the initial voltage of the neutral point of the inverter unit (406); Y If the highest value of the voltages between the positive electrodes of all the N-type photovoltaic panel chains and ground is greater than zero volts, adjust the on / off of power components in the inverter unit (406) according to the initial voltage and the highest value of the voltages between the positive electrodes of all the N-type photovoltaic panel chains and ground, to control the inverter unit (406) to provide the first alternating current voltage, where the peak amplitude of the first alternating current voltage is greater than the peak amplitude of the second alternating current voltage, in order to discharge the inverter unit (406), to reduce the neutral point voltage of the inverter's alternating current side (20) , so that the highest value of the voltages between the positive electrodes of the N-type photovoltaic panel chains and ground is less than or equal to zero volts.